In a wireless network, in which a network infrastructure does not exist, such as an ad hoc peer to peer network, a terminal is faced with a number of challenges when establishing a communication link with another peer terminal. One challenge is that when a terminal just powers up or moves into a new area, the terminal may have to first find out whether another terminal is present in the vicinity before any communication between the two terminals can start.
The general solution to the above problem of identification and acquisition is to let the terminal transmit and/or receive signals according to a communication protocol. However, an ad hoc network presents a number of challenges. Often the terminals may not have a common timing reference, e.g., because of the lack of the network infrastructure. As such, it is possible that when a first terminal is transmitting a signal and a second terminal is not in the receiving mode, the transmitted signal does not help the second terminal to detect the presence of the first terminal.
Half-duplex terminals present another challenge in that they are incapable of transmitting and receiving simultaneously. In such case, each of two terminals could be transmitting a message at the same time and may not be able to detect the presence of the other terminal because it could not receive the other terminal's signal at the time it is transmitting. These issues not only impact peer detection, but also impact other communications such as user scheduling, among others.
Finally, power efficiency has great impact on the battery life of the terminals and is thus another important consideration in any wireless system.